A fuel gauge is an instrument used to indicate the level of fuel contained in a tank. Although commonly used in automobiles, similar gauges can also be used to determine the substance level for any tank including underground fuel storage tanks.
When used in automobiles, the fuel gauge typically consists of two parts: the sensing unit and the indicator. The sensing unit usually uses a float connected to a potentiometer. The indicator is usually mounted in a dashboard of modern automobiles and typically includes a needle calibrated to point to a scale consisting of printed ink designed as a metered analog gauge with a needle indicating the level of fuel that remains in a tank based on where the needle is pointing to on the gauge. As the tank empties, the float drops and slides a moving contact along a resistor, increasing its resistance. In addition, when the resistance is at a certain point, it will also typically turn on a “low fuel” light on some vehicles.
There are many problems with the current state of the art for liquid level measurement. The principle problem is that the float system is not linear. When the float is horizontal it accurately measures the level of fluid in the tank. As the float becomes more vertical, it is no longer accurate. Also, irregularities in the shape and position of the tank may affect the accuracy of the system. Therefore there is a need for another safer, non-contact based method for fuel level to be determined. Modern vehicles usually have a computer that calculates “miles to empty”, but the older system of electrical measurement causes wild fluctuations in the calculations; therefore, a vehicle operator cannot completely rely on the accuracy of the system when planning a future stop to refuel.
Helmholtz resonance is the phenomenon of air resonance within a cavity such as the noise that occurs when one blows across the top of an empty bottle. The air in the port or tube (also referred to as the neck of the chamber) has mass and friction with the walls of the tube. A longer tube would make for a larger mass and more friction and vice-versa. The diameter of the tube is also related to the mass of air. The resonance of a bottle can change as liquid is added inside the bottle. The present inventor believes that Helmholtz resonance can be used to measure substance by measuring the unfilled space (unfilled with respect to a substance, but containing a vapor) in a container allowing the calculation of the amount of substance filling the container, which is the primary goal of the present invention, for which details will now be further described below. Resonant signals vary in frequency and amplitude.